<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body{
            margin: 0;
        }
        nav{
            width: 100%;
            height: 50px;
            display: flex;
            position: fixed;
            bottom: 0;
            background-color: #f1f1f1;
        }
        nav div{
            flex: 1;
            text-align: center;
            line-height: 50px;
        }
        .red{
            background-color: red;
            color: #fff;
        }
    </style>
</head>
<body>
    <div id="root">

    </div>
</body>
<script src="../react.js"></script>
<script src="../react-dom.js"></script>
<script src="https://cdn.staticfile.org/babel-standalone/6.26.0/babel.min.js"></script>
<script type="text/babel">
    class App extends React.Component{
        state={
            navList:["首页","分类","购物车","我的"],
            activeIndex:0
        }
        render(){
            let {activeIndex} = this.state;
            return (
                <div>
                    {activeIndex===0 && <Home/>}
                    {activeIndex===1 && <Cate/>}
                    {activeIndex===2 && <Cart/>}
                    {activeIndex===3 && <Mine/>}
                  <nav>
                    {
                        this.state.navList.map((item,index)=>{
                            return  <div key={index} onClick={()=>{
                                this.setState({
                                    activeIndex:index
                                })
                            }} className={activeIndex===index?'red':''}>{item}</div>
                        })
                    }
                  </nav>    
                </div>
            )
        }
    }
    class Home extends React.Component{
        render(){
            return (
                <h1>首页</h1>
            )
        }
    }
    class Cate extends React.Component{
        render(){
            return (
                <h1>分类</h1>
            )
        }
    }
    class Cart extends React.Component{
        render(){
            return (
                <h1>购物车</h1>
            )
        }
    }
    class Mine extends React.Component{
        render(){
            return (
                <h1>我的</h1>
            )
        }
    }

    ReactDOM.render(<App/>,document.getElementById("root"))
</script>
</html>